When this class is used from with in C#, all the appropriate comments and descriptions show up in the IntelliSense for Class1.DoStuff1 and Class1.DoStuff2, but none of the information from the XML comments show up in IntelliSense for Class1.DoStuff3 or Class1.DoStuff4

I also tried enabling 'Validate InteliSense' in the XML Document Generator options in the C++ project configuration properties but the output window shows xdcmake not recognizing /validate as a valid option.

I am currently using Visual Studio 2005 Team System for Software Developers(SP1) on XP-x64

It looks like you've uncovered a bug. I just tried this on our end and I see the problem as well. You can mitigate this by opening up the XML file generated and removing the "`1" part of the comment. Oh and you have two slashes in your last <//summary>.

It turns out you also uncovered another bug, which is that we expose the /validate option, which itself is not valid! Please log these bugs on our feedback site: http://connect.microsoft.com